1. Field of the Invention
This invention relates to a method of manufacturing a thin metal sheet directly from molten metal and an apparatus for manufacturing the same and, more particularly, to a method of manufacturing a thin metal sheet having an excellent surface character by continuously supplying a laminar flow having a constant shape of molten metal to a space between a pair of rollers and an apparatus for manufacturing the same.
2. Description of the Prior Art
Various methods and apparatuses for manufacturing a thin metal sheet directly from molten metal using a pair of rollers have been proposed.
For example, Japanese Patent Publication No. Sho 60-11584 discloses a continuous casting equipment, in which a gutter body is provided inclinedly, a molten metal inlet is provided at a higher level end of the gutter body, a dam or barrage for retaining charged molten metal is provided near the higher level end of the gutter body, a molten metal overflow section is provided adjacent to the lower level end of the gutter body, a cooling system for adequately cooling the molten metal flowing along the gutter body is provided, a mold consisting of a pair of rollers is provided at a suitable position below the molten metal overflow section, the higher level end of the gutter body is rotatably coupled by a pin to a stationary member, and a piston-and-cylinder assembly for turning the gutter body upwards and downwards about the pin is provided. Japanese Patent Laid-open No. Sho 55-100850 discloses a method of manufacturing an amorphous metal sheet by supplying molten metal onto the surface of a quick solidification roller or into a space between rollers for solidification, in which molten metal issuing from a nozzle is caused to strike an end portion of a base member having a flat or curved surface and then rendered into a molten metal flow having a predetermined flow width which is continuously supplied to the roller or rollers. Japanese Patent Laid-open No. Sho 60-130455 discloses a method of manufacturing a quickly cooled thin metal sheet by supplying molten metal from a nozzle toward the periphery of a high thermal conductivity material roller rotating at a high speed and solidifying the supplied molten metal by removal of heat due to contact with the roller to thereby obtain the thin metal sheet, in which the supplied flow of molten metal is rendered into a wide thin laminar flow before being fed to the roller periphery with a flat relay guide of a heat-resisting material provided between the nozzle and the roller for causing a slight deflection of the supplied molten metal flow.
With the continuous casting equipment disclosed in Japanese Patent Publication No. Sho 60-11584, it is difficult to control the flow rate. If the flow rate is insufficient, a phenomenon of narrowing the shape of flow even if charged a metal laminar flow having a width of a water-cooled roller readily occurs due to the surface tension. Further, the impact force of the flow is locally concentrated in a molten metal pool between water-cooled rollers. Therefore, there occur great variations of the molten metal level and resultant great disturbances of the molten metal flow. Consequently, a large number of wrinkles are formed on the surface of the obtained thin metal sheet. Further, the temperature distribution of the thin metal sheet immediately after emerging from the discharged rollers is not uniform. Therefore, cracks are inevitably formed in portions at high temperature. Further, with a prior art method of manufacturing an amorphous alloy, it has been difficult to manufacture a metal sheet having a large width. In the Japanese Patent Laid-open No. Sho 55-100850 noted above, it is disclosed that a wide metal sheet may be obtained by causing molten metal flow issued from a nozzle to strike an end portion of a base platen to form a wide molten metal flow and then quickly solidifying the molten metal by means of the roller. This method, however, has a problem that it is impossible to manufacture a very thin amorphous metal sheet with a thickness of 30 .mu.m and a width of 30 mm, for instance.
According to the invention disclosed in the Japanese Patent Laid-open No. Sho 60-130455 noted above, molten metal is supplied toward the roller periphery to the nozzle. Therefore, when the molten metal strikes the roller periphery, it is partly spattered to be attached to and solidified on the surface of a quickly cooled thin metal sheet being manufactured. Therefore, the surface smoothness of the thin metal sheet is insufficient.
An object of the present invention is to provide a method and an apparatus, which may preclude or overcome the various problems discussed above inherent in the prior art.